Prior art teaches several types of location tracking systems. Satellite based tracking systems, e.g. Global Positioning System (GPS), are probably the most common location tracking systems. However, their problem is that they are not suitable for indoor location tracking, because GPS signals do not penetrate building walls. For indoors location tracking, prior art teaches systems that utilize a pico network of wireless base stations, and the location of a given person in the coverage area of the pico network is determined on the basis of which wireless base station currently serves a personal communication device of the person. Other prior art systems rely on radio frequency identification technology or other radio communication technology, wherein a plurality of nodes disposed throughout an area are used to track locations of mobile devices.
A problem with prior art systems is that they are designed to operate in an environment having properties that exist during an installation phase of the location tracking system. However, in many scenarios the environment is subject to constant changes, e.g. contents of a warehouse or a layout of a cubicle office may change all the time. This results in that objects appear and disappear in arbitrary locations in the area, which may cause dead zones in the area, for example.